The present invention relates to digital scan conversion in an ultrasonic system, and more particularly, to a digital scan conversion method and apparatus for interpolating sampled data whose position is represented by a polar coordinate system, and thus calculating pixel data whose position is represented by a rectangular coordinate system.
A general ultrasonic system emits an ultrasonic signal to an object to be tested, and receives and samples the ultrasonic signal reflected from the object at a predetermined period, to thereby obtain tested data. A digital scan converter used in the ultrasonic system has various functions such as image information display and image processing, in addition to a basic function for storing the ultrasonic signal acquired from the object to be tested, and supplying the stored data to a display device. The digital scan converter stores digital data obtained from the ultrasonic signal according to scan modes provided by the ultrasonic system, for example, a B mode, an M mode, a D mode, a CD mode, in a memory, and reads the data stored in the memory if necessary, to then display the read data via a display device.
A conventional ultrasonic system uses coordinate conversion in order to represent data whose position is represented by a polar coordinate system into that represented by a rectangular coordinate system. The coordinate conversion creates degradation of picture quality and artifact. To solve this problem, many studies for interpolating a pixel position having no data on a rectangular coordinate system and filling data therein have been performed.
FIG. 1 is a graphical view for explaining an interpolation method which is performed in a conventional digital scan converter. In FIG. 1, a symbol ".largecircle." represents an actual sampling point which is positioned on a scan line represented by a polar coordinate system, and a symbol ".diamond." represents a pixel point on which data stored in a memory is displayed. The data in the pixel points (I.sub.0, I.sub.1) shown in FIG. 1 is calculated using a predetermined interpolation equation which is made by four data sampled at the sampling points A, B, C and D on mutually neighboring scan lines and a distant ratio between the sampling points A, B, C and D. However, such an interpolation method is not ideal but approximates only an ideal interpolation method, and thus remains the degradation of picture quality and artifact.